This invention relates to apparatus for use in control and metering of Pay-television signals over a cable network. Most Pay TV systems employed to date require that the Premium signals be scrambled to prevent reception by unauthorized cable TV subscribers. Authorized subscribers pay for the premium programming on a flat fee basis. Such systems have had a difficult time in the marketplace because of the high cost for the sophisticated descrambling equipment, or the unauthorized use of descrambling equipment where inexpensive scrambling systems are employed by the cable TV operator, and/or, the uncertainty of the value of the premium services to non-pay TV subscribers in view of the required flat rate payment commitment.
Other Pay-for-Use proposals such a Spencer (U.S. Pat. No. 3,504,109), Eisele (U.S. Pat. No. 3,368,031), Sargent (U.S. Pat. No. 3,335,421) and Murphy (U.S. Pat. No. 3,989,887) have failed to make an impact because of the high cost of their implementation. Spencer requires additional wiring be installed in each subscriber's residence; and Sargent proposes the D.C. power for system control be provided from the cable operators studio, most existing cable systems do not allow D.C. (or utility frequency A.C.) power to pass unhindered from the operator's studio into the subscriber's home. In addition both Sargent and Eisele do not allow for both premium pay services and normal cable TV services being distributed on the same coaxial distribution system.
Murphy does allow for such an arrangement but specifies the use of JAMMING circuitry that generates undesirable radio frequency energy. Also because of the jamming method employed Murphy's system is cumbersome to implement as it requires the use of one filter for each channel to be jammed. The use of low-cost commonly available broadband multichannel band blocking filters is precluded. Murphy had not foreseen the need to custom tailor each subscribers filtering arrangement, or the need to switch 6 to 15 channels simultaneously. Why Murphy chose to employ jamming circuitry is uncertain, but from the circuitry shown in his patent it appears that he could not obtain adequate filtered channel insertion loss and thus was forced to jam the channel as well as filter it. His patent fails to instruct any method of keeping the level of a filtered channel 50 dB below that of the unfiltered channel as his system does not require such. In addition to extensive trap filter circuitry and jamming circuits, Murphy also requires simultaneously positive and negative power to operate his apparatus making it expensive for a one unit per home installation. None of these systems make allowance for parental control requirements, simultaneous viewing of 2 or more premium services, multiple-point operation, and control by external apparatus such as video recorders and simple timers. Murphy and the others have also not foreseen the need to employ sampling or preview circuitry to stimulate impulse buying.
DiLorenzo (U.S. Pat. No. 4,317,213) teaches how Parental Lockout may be accomplished through the generation and transmission of interfering radio frequencies, he does not instruct how it could be accomplished to the satisfaction of radio spectrum regulatory agency requirements. Rifken (U.S. Pat. No. 4,272,791) illustrates a scheme to permit the simultaneous recording of a Premium TV channel and viewing of a non-scrambled channel, or vice-versa. Rifken's solution solves a problem that subscribers with VCRs have if their premium programming is scrambled but is not applicable to the apparatus embodied in this invention as no scrambling is required. Rifken foresees no requirement for the VCR to control any switching apparatus.